A novel finding from researchers supported in part by NIEHS shows that lead exposures in early childhood are associated with increased risk for sleep problems and excessive daytime sleepiness in later childhood. This is the first long-term, population-based study to examine links between early lead exposures and sleep problems.
The research, published in the December issue of the journal SLEEP, used data from more than 1,400 children in the Chinese city of Jintan. They were part of a study, which began in 2004, investigating the influence of lead exposure on neurocognitive, behavioral, and health outcomes in children and adolescents.
Lead pollution is pervasive throughout China and other developing countries, and though rates of lead exposure are decreasing due to the phase-out of leaded gasoline and increased public awareness, it still presents a significant health risk to children.
Important but neglected topic
“Little is known about the impact of heavy metals exposure on children’s sleep, but the study’s findings highlight that environmental toxins, such as lead, are important pediatric risk factors for sleep disturbance,” said the study’s lead author Jianghong Liu, Ph.D., associate professor at the University of Pennsylvania School of Nursing, and a faculty member at the university’s Perelman School of Medicine.
Adverse health outcomes associated with sleep problems include developmental disorders, and intellectual and neurocognitive problems, according to the study authors, which included colleagues in China.
Children with higher lead levels reported more problems
Researchers assessed the blood levels of 665 children ages 3-5, and evaluated sleep habits six years later. The children and their parents answered separate questionnaires. The children in the study reported excessive daytime sleepiness, insomnia, early morning awakening, trouble initiating and maintaining sleep, and having to use sleeping pills.
Child-reported insomnia and use of sleeping pills were two times and three times more prevalent in children with blood lead levels greater than or equal to 10 micrograms per deciliter than in children with lower levels. Although the findings did not hold for parent-reported sleep problems, the authors said that for older children, it is to be expected that parents may report lower levels of sleep problems, such as excessive daytime sleepiness, than the children do, due to less daytime contact as the children grow older.
Environmental factors need more study
“Insufficient sleep and daytime sleepiness is very prevalent in children and adolescents, and it is a pervasive problem that is linked with a significant public health burden,” explained Liu. “More research needs to be done to identify contributing factors and ways to prevent or reduce their impact.”
“This study addresses an important but often neglected area of sleep science, namely, environmental factors that disrupt sleep biology and behavior in children and other vulnerable populations,” said the study’s senior researcher David Dinges, Ph.D., head of the Perelman School of Medicine Division of Sleep and Chronobiology.
Citation: Liu J, Liu X, Pak V, Wang Y, Yan C, Pinto-Martin J, Dinges D. 2015. Early blood lead levels and sleep disturbance in preadolescence. Sleep 38(12):1869–1874.
(This story is based on a University of Pennsylvania School of Nursing press release.)